1. Field of the Invention
The invention relates generally to radar systems for earth probing and, more particularly, but not by way of limitation, it relates to an improved method and apparatus for use in surveillance and hazard protection in and around coal in situ and at the coal seam work face.
2. Description of the Prior Art
There have been previous attempts to use radar to explore geologic materials, but most of this work has been unsuccessful except when used in salt or extremely dry formations. In most previous operations the approach has been to apply radar technology as developed by the Aerospace industry with direct application to ground probing. The methods of recording and subsequent signal processing that have been utilized in the Aerospace industry were directed toward enhancing system signal to noise in the presence of random noise, and they produced reliable indication only at very short depths of penetration, on the order of a few feet. These efforts are exemplified by U.S. Pat. Nos. 3,806,795; 3,831,173; and 4,072,942. In a more recent development, U.S. Pat. No. 4,008,469 discloses a hybrid short pulse radar system for earth probing, but here again the digital processing scheme is directed toward enhancing system signal to noise in the presence of random noise. No prior art teaching for earth probing radar is directed to overcoming the problem of source coherent noise or interference, i.e., multiples and other reflections from undesired objectives.